The total template activity and the relative abundance of nine different bacteriophage T7 messenger RNAs has been measured throughout infection of T7-infected male and female cells by measuring quantitatively the amount of gene-specific polypeptide synthesized in S-30 extracts prepared from uninfected Escherichia coli cells. The total template activity of RNA extracted from two T7-infected male strains, E. coli 279/F′ and E. cli RV/F′, is 20% and 50%, respectively, of the template activity in RNA extracted from T7-infected, isogenic female strains. At the individual mRNA level, there is not a uniform reduction in the level of the nine different messenger RNAs assayed. The early messages for T7 RNA polymerase and the gene 0.3 protein are present in equal amounts at early times in infected male and female cells. At late times there is a higher apparent concentration of 0.3 mRNA in male cells. Among the late proteins there is a wide variation in relative mRNA abundance in male cells. The mRNA for T7 lysozyme is present in equal amounts in male and female cells. The late mRNAs encoded by genes 6, DUP, 8, 9, 10 and 15 are present in RNA extracted from male cells at concentrations ranging from 5 to 100% of their level in female cells. The messenger RNAs corresponding to genes 16, 17 and 19 have not been detected in RNA from male cells although they can be detected in RNA from female cells. The mRNA from gene 12 is present in RNA from male cells but at a concentration too low to measure accurately. The relative amount of individual T7 mRNAs is lower in E. coli 279/F′ than it is in RV/F′, but there is a qualitative consistency in the degree of reduction in the two male strains. When S-30 extracts of T7-infected male and female cells are compared for their ability to translate added T7 early or late mRNA, there is an insignificant difference between the two extracts. Both are able to translate late T7 mRNAs with approximately equal efficiency. This efficiency is similar to the efficiency of translation in an S-30 extract prepared from uninfected male or female cells. Thus it appears that there is no specific translational discrimination against late T7 mRNAs in infected or uninfected male E. coli cell extracts. The unknown cause of the abortive T7 infection of male cells appears to reduce the synthesis of certain late T7 messenger RNAs as well as reducing total late protein synthesis.